1. Field of the Invention
Embodiments of the invention relate generally to instruments for use in orthopedic surgery, and more particularly to instruments for use in total hip arthroplasty.
2. Background of the Invention
Minimally invasive surgery techniques have become popular in total hip arthroplasty (THA) surgery. Advantages include minimizing soft tissue damage, reducing recovery and healing time, and reducing the length of stay in hospital. One version of such minimally invasive THA techniques is the so-called “anterior approach” or “direct anterior approach” which uses, for instance, a portal between the tensor fascia latae muscle and the rectus femoris muscle. This approach can exploit the interval between those muscles for both acetabular and femoral preparation, allow for primary exposure of the hip joint capsule with minimization of muscle damage, limit incision length, and leverage other advantages.
Exposure of the proximal femoral intramedullary canal in order to prepare the canal to receive the femoral stem can be problematic in such anterior approach THA's, however. Generally, the subject leg can be positioned in extension, external rotation and adduction. The proximal femur can be levered using wing retractors for further exposure of the intramedullary canal to access through the generally shorter than conventional incision. Anatomical features of some patients, such as gut or muscle tissue, can nevertheless present problems in accessing and preparing the femoral canal through the smaller incision. More particularly, leverage of the proximal femur to correct orientation relative to the incision and levering of an instrument directly through the incision to prepare the intramedullary canal can be obstructed by the gut or musculature of some obese or muscular patients. Special instrument handles have been developed for such cases which include anterior and lateral offsets. The bone shaping member, such as a broach or an osteotome, may be connected to the distal end of such a handle, inserted through the incision into the intramedullary canal of the femur, and manipulated to avoid the gut or other musculature by virtue of the anterior and lateral offsets of the handle. See, e.g., M. Nogler, et al., A Double Offset Shaping Member Handle for Preparation of the Femoral Cavity in Minimally Invasive Direct Anterior Total Hip Arthroplasty, 21 J. Arthroplasty, pp. 1206-1208 (No. 8, 2006); U.S. Ser. No. 10/991,641 filed Nov. 18, 2004 entitled “Surgical Technique and Instrumentation for Minimal Incision Hip Arthroplasty Surgery;” and U.S. Ser. No. 12/412,527 filed Mar. 27, 2009 entitled “Surgical Technique and Instrumentation for Minimal Incision Hip Arthroplasty Surgery.” All three of these documents are incorporated herein by this reference.
Such instruments are physically large and heavy however, and separate instruments are required for each of the right and left femurs in order to provide the required lateral offset. Consequent issues include those related to, among other things, logistics, inventory requirement, and expense.